The present invention relates to connectors used between coaxial signal lines and microwave frequency slab lines, and more particularly to a coax to slab line connector with improved inner conductor captivation and reduced insertion loss variation. The present invention further relates to programmable microwave attenuators using such coax to slab line connectors.
Conventional coax to slab line connectors are modified standard female coax connectors in which the folded over end of a slab line inner conductor is pressed into a slot cut into the termination end of the cylindrical coax inner conductor to form a spring contact. This conventional arrangement results in a mechanically unreliable connection in which the slab line inner conductor is disturbed whenever an external mating connector is connected or disconnected.
At sufficiently high microwave frequencies, when the wavelength is less than about twice the slab line cavity depth, undesirable, frequency dependent coupling losses occur as a result of unwanted modes of microwave energy transmission. For example, with a typical slab line cavity depth of 0.5 inches (1.28 cm) some energy is lost at frequencies above about 11.8 GigaHertz as a result of multiple reflections in the TE.sub.10 mode of transmission. The magnitude of this insertion loss is frequency dependent.
Therefore, what is desired is a coax to slab line connector, and a programmable microwave attenuator using such connectors, that provides mechanically reliable connection with insertion losses relatively independent of frequency.